In modern motor vehicles, ever more functions are implemented using electrical components. This causes an ever rising requirement for electrical power. In order to cover this requirement, the efficiency of the generator system in the motor vehicle has to be increased.
Up to now, pn diodes have been used, as a rule, as Z diodes in the motor vehicle generator system as rectifiers. The advantages of the pn diodes are low blocking-state current and robustness. The main disadvantage of pn diodes is the high forward voltage UF. At room temperature, the current only begins to flow at UF=0.7V. And under normal operating conditions, for instance, at a current density of 500 A/cm2, UF rises to over 1 V, which means a nonnegligible loss in efficiency.
In theory, the Schottky diode is available as an alternative. Schottky diodes have a clearly lower forward voltage than pn diodes, such as 0.5 V to 0.6 V at a high current density of 500 A/cm2. In addition, Schottky diodes, as majority carrier components, offer advantages in rapid switching operation. The use of Schottky diodes in motor vehicle generator systems has, however, still not taken place. This must be attributed to a few decisive disadvantages of Schottky diodes: 1) higher blocking-state current in comparison to pn diodes, 2) strong dependence of the blocking-state current of the reverse voltage, and 3) poor robustness, especially at high temperature.
The usual Schottky diodes can be changed in their electrical properties by applying trenches implemented by etching. Such further developed Schottky diodes are also designated as trench-Schottky-barrier-Schottky diodes (TSBS). An example of such a conventional semiconductor device is shown in FIG. 1. However, the conventional trench-Schottky-barrier-Schottky diodes do not have the requisite robustness they need in order to be used as Z diodes in motor vehicle generator systems.